There are innumerable patents in the field of textile cutting or the like using stationary tables and numerical controls. When moving tables were designed to make the material move forward for cutting by sections, vacuum gripping was employed and the problem of sealing to maintain the vacuum clamping led to completely closing the conveyor table converting it into a sealed box with the top part opened. After inserting the material, the box was closed with an airtight material which was normally discarded after the cutting tool had passed. With such a system, the problem of sealing the ends of the cutting table does not arise as they are located within the large vacuum box. Applications of this technology are disclosed, e.g., in Gerber Garment Technology, Inc. Spanish Patent Nos. 520,922; 520,923; and 520,924; and Strumpf U.S. Pat. No. 4,322,993.
One disadvantage of this system is that the vacuum box must be very rugged, since due to the vacuum levels used and the relatively large surfaces, very high force levels result.
Another solution is to create an airtight chamber under the cutting surface, and through horizontal and vertical mechanical valving, to form independent vacuum sections. See, e.g., Gerber Garment Technology, Inc. U.S. Pat. Nos. 4,485,712 and 4,528,878. The complications of using this method with cutting tables results in the solution being frequently rejected for economic reasons.
An alternative solution is to insert some type of discardable panel which cuts the flow horizontally such as that disclosed in Gerber Garment Technology Inc., U.S. Pat. No. 3,765,289. After the cutting knife has passed, the panels are changed as they become ineffective.
U.S. Patent Application Ser. No. 132,999 filed Dec. 15, 1987 entitled "Improved Vacuum Grip Cutting Table", the disclosure of which is incorporated herein by reference, discloses a conveyor table for cutting laminar material. The conveyor table comprises a conveyor loop formed by a plurality of successive adjacent tiles. The cutting surface defined by the tiles located in the upper horizontal conveyor leg comprises a mat which is penetratable by a knife and permeable to air. A vacuum is applied to the mats in the upper horizontal conveyor leg to secure the material to be cut. At the curvature adjacent the material feed end and the material collection end of the upper horizontal conveyor leg, air or vacuum leakage occurs, i.e., air passes from the atmosphere into the vacuum area. This causes the vacuum pump to operate at an excessive flow rate and/or a reduction in the vacuum.
Due to the work cycle of the movable conveyor table, the table advances at a variable pace depending on the configuration to be cut in the material and the location of the material in the cutting work window. Consequently, any closing system at the feed end and collection end of the upper horizontal conveyor leg cannot be limited to two fixed positions, open and closed. The closing system must have the necessary flexibility to adjust to the variable movement and starting and stopping of the conveyor loop.